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Abstract:

A first image obtained by capturing white paper placed under an illuminant
having known illuminant information using an image capturing device is
input together with identification information of the illuminant, and
illuminant information of the illuminant having the known illuminant
information is obtained together with the identification information of
the illuminant. A table is generated by associating a chromaticity of the
first image with the obtained illuminant information based on the
identification information. A second image obtained by capturing the
white paper placed under an illuminant having unknown illuminant
information using the image capturing device is input, and illuminant
information of the illuminant having the unknown illuminant information
is estimated from a chromaticity of the second image by referring to the
table.

Claims:

1. A color processing apparatus comprising:a first inputting section,
configured to input a first image obtained by capturing a white paper
placed under an illuminant having known illuminant information using an
image capturing device, together with identification information of the
illuminant;an analyzer, configured to analyze a chromaticity of an
image;an obtaining section, arranged to obtain illuminant information of
the illuminant having the known illuminant information, together with the
identification information of the illuminant;a generator, configured to
generate a table obtained by associating the chromaticity of the first
image analyzed by said analyzer with the obtained illuminant information
based on the identification information;a second inputting section,
configured to input a second image obtained by capturing the white paper
placed under an illuminant having unknown illuminant information using
the image capturing device; andan estimator, configured to estimate, by
referring to the table, illuminant information of the illuminant having
the unknown illuminant information from chromaticity of the second image
analyzed by said analyzer.

2. The apparatus according to claim 1, further comprising a monitor
arranged to display the estimated illuminant information.

3. The apparatus according to claim 1, wherein the illuminant information
is a color temperature.

4. The apparatus according to claim 1, wherein the illuminant information
is a spectral type.

5. The apparatus according to claim 1, wherein said generator generates
the table for each model of image capturing device.

6. The apparatus according to claim 1, wherein said generator generates
the table for each type of white paper.

7. An image processing apparatus comprising:a memory which stores a table
generated by a color processing apparatus according to claim 1;a
capturing section, configured to capture white paper placed under an
illuminant having unknown illuminant information;an analyzer, configured
to analyze a chromaticity of an image of the white paper captured by said
capturing section; andan estimator, configured to estimate, by referring
to the table, illuminant information of the illuminant having the unknown
illuminant information from the chromaticity analyzed by said analyzer.

8. The apparatus according to claim 7, further comprising a monitor
arranged to display the estimated illuminant information.

9. A color processing method, which is carried out in an information
processing apparatus, the method comprising the steps of:inputting a
first image obtained by capturing a white paper placed under an
illuminant having known illuminant information using an image capturing
device, together with identification information of the
illuminant;analyzing a chromaticity of an image;obtaining illuminant
information of the illuminant having the known illuminant information,
together with the identification information of the illuminant;generating
a table obtained by associating the chromaticity of the first image
analyzed in the analyzing step with the obtained illuminant information
based on the identification information;inputting a second image obtained
by capturing the white paper placed under an illuminant having unknown
illuminant information using the image capturing device; andestimating,
by referring to the table, illuminant information of the illuminant
having the unknown illuminant information from chromaticity of the second
image analyzed in the analyzing step.

10. An image processing method, which is carried out in an information
processing apparatus, the method comprising the steps of:storing a table
generated in a color processing method according to claim 9 into a
memory;capturing white paper placed under an illuminant having unknown
illuminant information;analyzing a chromaticity of an image of the white
paper captured in the capturing step; andestimating, by referring to the
table, illuminant information of the illuminant having the unknown
illuminant information from the chromaticity analyzed in the analyzing
step.

11. A computer-readable storage medium storing a computer-executable
program for causing a computer to perform a color processing method, the
method comprising the steps of:inputting a first image obtained by
capturing a white paper placed under an illuminant having known
illuminant information using an image capturing device, together with
identification information of the illuminant;analyzing a chromaticity of
an image;obtaining illuminant information of the illuminant having the
known illuminant information, together with the identification
information of the illuminant;generating a table obtained by associating
the chromaticity of the first image analyzed in the analyzing step with
the obtained illuminant information based on the identification
information;inputting a second image obtained by capturing the white
paper, placed under an illuminant having unknown illuminant information,
using the image capturing device; andestimating, by referring to the
table, illuminant information of the illuminant having the unknown
illuminant information from chromaticity of the second image analyzed in
the analyzing step.

12. A computer-readable storage medium storing a computer-executable
program for causing a computer to perform an image processing method, the
method comprising the steps of:storing a table generated in a color
processing method according to claim 9 into a memory;capturing white
paper placed under an illuminant having unknown illuminant
information;analyzing a chromaticity of an image of the white paper
captured in the capturing step; andestimating, by referring to the table,
illuminant information of the illuminant having the unknown illuminant
information from the chromaticity analyzed in the analyzing step.

[0004]As a process for estimating illuminant information of an illuminant
represented by a fluorescent lamp, a process using a spectroradiometer is
generally available. This is a process for estimating the illuminant
information by measuring the spectral characteristics of an illuminant
using a spectroradiometer and analyzing it. When an illuminant is a
fluorescent lamp, its illuminant information can be obtained from a light
color symbol described in the model of the fluorescent lamp. In addition,
there is available a technique of restoring the spectral reflectance of
an object from a sensor signal of an image capturing unit such as a
digital still camera and estimating illuminant information using
anomalous reflection (for example, see Japanese Patent Laid-Open No.
2004-177396).

[0005]Illuminant information will be defined herein. The color temperature
and spectral type of an illuminant are referred to as illuminant
information, hereinafter. Note that a spectral type represents the type
of distribution of light emission wavelengths of a fluorescent lamp, that
is, a broad-band type, three-band type, and normal type.

[0006]To obtain illuminant information using a spectroradiometer, purchase
of illuminant measuring equipment is necessary. However, such equipment
is expensive in general. For an end user of an image processing
apparatus, it is difficult to readily obtain illuminant information by
measurement since purchase of equipment forms a barrier against it.

[0007]A method of obtaining illuminant information from the model of
fluorescent lamp can obtain color temperatures set as spec values, but
cannot obtain the color temperature of a fluorescent lamp that has
degraded due to aging. In addition, lighting equipment which uses
fluorescent lamps often have lampshades attached to them. Since they
conceal the model of the fluorescent lamp from users, it is sometimes
difficult to obtain illuminant information from the model. In addition,
there is an indirect lighting type lighting equipment in which the light
of a fluorescent lamp does not directly come outside due to a lampshade.
A color and material differ in respective lampshades, and the color
temperature of light reflected by or transmitted through a lampshade is
sometimes different from the spec value of the fluorescent lamp.

[0008]A technique disclosed in Japanese Patent Laid-Open No. 2004-177396
(U.S. Pat. No. 7,206,072) requires an image capturing unit which has four
sensors of R, G, B, and X. When an image capturing equipment having such
an image capturing unit is not available, illuminant information cannot
be obtained.

SUMMARY OF THE INVENTION

[0009]In one aspect, a color processing method comprises the steps of:
inputting a first image obtained by capturing a white paper placed under
an illuminant having known illuminant information using an image
capturing device, together with identification information of the
illuminant; analyzing a chromaticity of an image; obtaining illuminant
information of the illuminant having the known illuminant information,
together with the identification information of the illuminant;
generating a table obtained by associating the chromaticity of the first
image analyzed in the analyzing step with the obtained illuminant
information based on the identification information; inputting a second
image obtained by capturing the white paper placed under an illuminant
having unknown illuminant information using the image capturing device;
and estimating, by referring to the table, illuminant information of the
illuminant having the unknown illuminant information from chromaticity of
the second image analyzed in the analyzing step.

[0010]According to the aspect, it is possible to estimate the illuminant
information of an illuminant having unknown illuminant information.

[0011]Further features of the present invention will become apparent from
the following description of exemplary embodiments with reference to the
attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a block diagram showing the arrangement of a color
processing apparatus of an embodiment.

[0019]FIG. 8 is a view illustrating an example of a color temperature DB.

[0020]FIG. 9 is a view for explaining color temperature estimating.

[0021]FIG. 10 is a view for explaining a capturing environment upon
capturing white paper.

[0022]FIG. 11 is a flowchart for explaining database referring.

[0023]FIG. 12 is a view for explaining spectral type-database generation.

[0024]FIG. 13 is a view illustrating an example of a spectral type DB.

[0025]FIG. 14 is a view for explaining spectral type estimating.

[0026]FIG. 15 is a flowchart for explaining database referring.

[0027]FIG. 16 is a view illustrating the back surface of a digital camera.

[0028]FIG. 17 is a view illustrating an example of a WB mode selection
menu.

[0029]FIG. 18 is a view for explaining a database for each model of
digital camera.

[0030]FIGS. 19 and 20 are views illustrating examples of a user interface
displayed on a monitor by color temperature/spectral type estimation
application software running on a color processing apparatus.

DESCRIPTION OF THE EMBODIMENTS

[0031]Color processing of embodiments according to the present invention
will be described below in detail with reference to the accompanying
drawings.

First Embodiment

[0032]FIG. 1 is a block diagram showing the arrangement of a color
processing apparatus of an embodiment.

[0033]Referring to FIG. 1, a microprocessor (CPU) 101 uses a random access
memory (RAM) 105 as a work memory to execute an operating system (OS) and
various programs stored in a read-only memory (ROM) 104 or a hard disk
drive (HDD) 106. The CPU 101 controls components (to be described later)
via a system bus 109 to execute color processing to be described later.

[0034]A Universal Serial Bus (USB) interface (I/F) 102 is an interface
which connects the color processing apparatus to a serial bus 110 such as
USB. As devices used by a user to input an instruction and the like to
the color processing apparatus, a keyboard 111 and a mouse 112 are
connected to the serial bus 110. A digital camera 114 and a printer (not
shown) can also be connected to the serial bus 110.

[0035]A video interface (I/f) 103 is an interface which connects the color
processing apparatus to a monitor 113.

[0036]In addition to the OS, a control program executed by the color
processing apparatus, a color processing program, and various data are
stored in the HDD 106. A card reader/writer 107 reads/writes data from/in
a memory card.

[0037]A process will be described below in which the color processing
apparatus uses the digital camera 114 to obtain the color temperature of
a fluorescent lamp whose color temperature is unknown. A process for
obtaining the color temperature of a fluorescent lamp using the digital
camera 114 can be broadly divided into two processes. One is a process
for generating a color temperature database (DB) of fluorescent lamp (to
be referred to as color temperature database generation, hereinafter),
and the other is a process for estimating the color temperature of a
fluorescent lamp, whose color temperature is unknown, by referring to the
color temperature DB (to be referred to as color temperature estimating,
hereinafter).

[0039]FIG. 3 is a view for explaining a capturing environment upon
capturing white paper.

[0040]A light booth 302 is placed in a room 301 which is shielded from
external light. White paper 304 is placed under a fluorescent lamp 303 in
the light booth 302, the fluorescent lamp 303 is turned on, and the white
paper 304 is captured using the digital camera 114. Upon capturing, care
is taken to make sure that the shadows of a photographer, digital camera
114 and other articles do not fall on the white paper 304, and the white
paper 304 is captured at a maximum angle of view. Of course, all
illuminations other than the fluorescent lamp 303 are turned off.

[0041]The fluorescent lamp 303 used to capture the white paper 304 is one
of fluorescent lamps of types to be registered in a color temperature
database (for example, fluorescent lamps of all types commercially
available). Note that when fluorescent lamps have the same color
temperature and spectral type but their makers or brands are different,
they are treated as different types.

[0042]In the white paper capture S201, one of fluorescent lamps of a
plurality of types is mounted in the light booth 302, and the white paper
304 is captured under the fluorescent lamp 303 three times. After
capturing the white paper 304 three times, the fluorescent lamp 303 is
changed to a fluorescent lamp of another type, and the white paper 304 is
similarly captured three times. When the white paper 304 has been
captured three times for each of all types of fluorescent lamp, the white
paper capture S201 ends.

[0044]The white paper 304 is put in the light booth 302 (S401), a
fluorescent lamp of an arbitrary type is mounted in the light booth 302
and turned on (S402), and the white balance (WB) of the digital camera
114 is set to "direct sunlight" (S403). The white paper 304 is captured
using the digital camera 114 at a maximum angle of view (S404). In
accordance with determination in step S405, the white paper 304 is
captured three times (S404).

[0045]After capturing the white paper 304 three times, it is determined
whether the white paper 304 has been captured under fluorescent lamps of
all types to be registered in a color temperature database (S406). If NO
in step S406, the fluorescent lamp 303 mounted in the light booth 302 is
changed to a fluorescent lamp of another type and the changed lamp is
turned on (S407), and the white paper 304 is captured three times again
(S404 and S405). Note that a fluorescent lamp of another type is of
course a fluorescent lamp under which the white paper 304 has not been
captured yet.

[0046]By repeating the capturing procedure described above, the captured
images of the white paper 304 are obtained by capturing the white paper
304 three times under each of fluorescent lamps of all types to be
registered in a color temperature database Of course, in order to
identify the type of fluorescent lamp under which image data has been
captured, for example, information (a maker name, model, and the like)
for identifying the type of fluorescent lamp is appended to the file name
of the image data of the captured image (first white paper image) of the
white paper 304.

Image Analysis

[0047]The image analysis S202 is a process executed by the CPU 101 of the
color processing apparatus for analyzing a white paper image captured in
the white paper capture S201.

[0048]FIG. 5 is a flowchart for explaining the image analysis S202.

[0049]The CPU 101 inputs the captured images (first white paper images) of
the white paper 304 from the digital camera 114 (first input), and stores
them in a predetermined area of the HDD 106 (S501). Image data can be
obtained from the digital camera 114 via the serial bus 110.
Alternatively, a memory card removed from the digital camera 114 may be
inserted into the card reader/writer 107 to obtain image data from the
memory card.

[0050]The CPU 101 then sets a region of interest (ROI) in the central
portion of one of the three images of the white paper 304 captured under
a given fluorescent lamp (S502), and calculates the average R, G, and B
values of the ROI (S503). Details of these steps will be described later.
The CPU 101 converts the average R, G, and B values into X, Y, and Z
values (S504) using:

[0052]The CPU 101 determines whether the x and y values of the three
images captured under a fluorescent lamp of a single type have been
obtained (S506). If NO in step S506, the CPU 101 returns the process to
step S502 and calculates the x and y values of the other image. After
calculating the x and y values of the three images, the CPU 101 stores
the average values of those x and y values in a predetermined area of the
HDD 106 as x and y values corresponding to the type of this fluorescent
lamp (S507).

[0053]The CPU 101 determines whether the average x and y values of the
captured images stored in the HDD 106 and corresponding to all types of
fluorescent lamp have been obtained (S508), and repeats the processes in
steps S502 to S507 until average x and y values corresponding to all
types of fluorescent lamp to be registered in a color temperature
database are obtained.

Setting of RIO

[0054]FIG. 6 is a view for explaining an example of an ROI setting method.

[0055]Letting W be the width of an image 601 and H be its height, the
width of an ROI 602 is represented by W/2; the height, H/2; and the area,
1/4 that of the image. Assuming that the lengths from the respective
sides of the image 601 to the corresponding sides of the ROI 602 are
represented by W/4 and H/4, respectively, the CPU 101 sets the ROI 602 in
the central portion of the image 601. The length between the
corresponding sides, that is, the position of the ROI 602 is not strictly
determined, and the ROI 602 only needs to be set in the almost central
portion of the image 601.

[0056]The ROI 602 is set while considering the possibility that the
brightness of the peripheral portion of a captured image drops due to a
decrease in peripheral brightness of a lens. This phenomenon occurs
depending on the lens used in capturing. To solve this problem, a
database of lenses may be prepared, and the position and area of the ROI
602 can be set based on the information of peripheral brightness of the
lens used in capturing, which is obtained from the database of lens.

Color Temperature Measurement

[0057]The color temperature measurement S203 is a process for measuring
using a spectroradiometer the color temperatures of fluorescent lamps of
all types used in the white paper capture S201 in the same environment as
in the white paper capture S201. Note that all illuminations other than
the fluorescent lamp 303 are turned off upon measurement.

[0059]A fluorescent lamp of an arbitrary type is mounted in the light
booth 302 and turned on (S701), and the color temperature of the
fluorescent lamp 303 is measured using a spectroradiometer (S702). In
accordance with determination in step S703, the color temperatures of
three fluorescent lamps of the same type are measured (S702). After
measurement of the color temperatures of the three fluorescent lamps of
the same type finishes, the average value (average color temperature) of
the measurement results and information for identifying the type of
fluorescent lamp (a maker name, model, and the like) are input to the
color processing apparatus via, for examples the keyboard 111 (S704). The
CPU 101 of the color processing apparatus stores the input average color
temperature and identification information in a predetermined area of the
HDD 106.

[0060]When measurement of the color temperatures of three fluorescent
lamps of the same type has finished, the CPU 101 determines whether the
color temperatures of the fluorescent lamps of all types to be registered
in a color temperature database have been measured (S705). If NO in step
S705, the fluorescent lamp 303 mounted in the light booth 302 is changed
to a fluorescent lamp of another type and the changed lamp is turned on
(S706). Then, measurement of the color temperatures of three fluorescent
lamps of the same type (S702 and S703) and input of a measurement result
(S704) are executed again.

[0061]By repeating the measurement procedure as described above, the color
temperatures of fluorescent lamps of all types used in the white paper
capture S201 are measured.

Data Link Process

[0062]The CPU 101 associates average x and y values corresponding to the
type of fluorescent lamp calculated in the image analysis S202 with an
average color temperature corresponding to the type of fluorescent lamp
input in the color temperature measurement S203 based on the
identification information to generate a table an example of which is
illustrated in FIG. 8. The CPU 101 stores the generated table in a
predetermined area of the HDD 106 as a color temperature database (DB)
401 illustrated in FIG. 2 (data link process S204).

[0063]In FIG. 8, "fluorescent lamp ID" indicates identification
information (ID) uniquely set for a fluorescent lamp of one type, and
LIGHT_MAX_COUNT indicates the maximum value of "fluorescent lamp ID",
that is, the number of types of fluorescent lamp.

[0065]FIG. 10 is a view for explaining a capturing environment upon
capturing white paper.

[0066]White paper 304 is placed under a fluorescent lamp 901 whose color
temperature is unknown, the fluorescent lamp 901 is turned on, and the
white paper 304 is captured using a digital camera 114 (white paper
capture S801). Upon capturing, care is take to make sure that the shadows
of a photographer, digital camera 114 and other articles do not fall on
the white paper 304, and the white paper 304 is captured at a maximum
angle of view.

[0067]As the white paper 304, it is preferable to use paper of the same
maker and same model as those of the white paper 304 used in color
temperature database generation. Likewise, as the digital camera 114, it
is preferable to use a digital camera of the same maker and same model as
those of the digital camera 114 used in color temperature database
generation. It is desirable to turn off all illuminations other than the
fluorescent lamp 901.

[0069]The image analysis S802 corresponds to steps S501 to S505 in the
flowchart of FIG. 5. That is, the CPU 101 inputs the captured image
(second white paper image) of the white paper 304 from the digital camera
114 (second input), and stores it in a predetermined area of the HDD 106
(S501). The CPU 101 then sets an ROI in the central portion of the
captured image (S502), calculates the average R, G, and B values of the
ROI (S503), converts the average R, G, and B values into X, Y, and Z
values (S504), and calculates chromaticity x and y values from the X, Y,
and Z values (S505).

[0070]From the above-described processes, x and y values are calculated
from the image data of white paper captured under the fluorescent lamp
901 whose color temperature is unknown. These x and y values are referred
to as "estimation target x and y values" hereinafter.

Database Referring

[0071]The database referring S803 is a process executed by the CPU 101 of
the color processing apparatus for estimating, by referring to the color
temperature DB 401, a color temperature corresponding to estimation
target x and y values calculated in the image analysis S802, that is, the
color temperature of the fluorescent lamp 901 whose color temperature is
unknown.

[0072]FIG. 11 is a flowchart for explaining the database referring S803.

[0073]The CPU 101 initializes a counter i to 1 (S1001), and calculates a
Euclidean distance Di between the estimation target x and y values and
the x and y values of each record in the color temperature DB 401 (S1002)
using:

Di= {(xi-x)2+(yi-y)2} (3)

where x and y are the estimation target x and y values, respectively, and

[0074]xi and yi are the x and y values of a fluorescent lamp ID=i ,
respectively.

[0075]Next, the CPU 101 increments the counter i (S1003), compares the
counter i with LIGHT_MAX_COUNT (S1004), and returns the process to step
S1002 when i≦LIGHT_MAX_COUNT.

[0076]When i>LIGHT_MAX_COUNT in step S1004, the CPU 101 initializes the
counter i to 1, a variable Min to D1, and a variable MinID to 1 (S1005).
The CPU 101 compares the variable Min with Di (S1006), and advances the
process to step S1008 when Min≦Di. When Min>Di, the CPU 101
updates the variable Min to Di and the variable MinID to i (S1007).

[0077]The CPU 101 increments the counter i (S1008), compares the counter i
with LIGHT_MAX_COUNT (S1009), and returns the process to step S1006 when
i≦LIGHT_MAX_COUNT.

[0078]When i>LIGHT_MAX_COUNT in step S1009, the CPU 101 obtains the
color temperature of the fluorescent lamp ID=MinID from the color
temperature DB 401. The CPU 101 executes a process such as displaying on
the monitor 113 the obtained color temperature as the estimated color
temperature of the fluorescent lamp 901 whose color temperature is
unknown (S1010).

[0079]In this manner, it is possible to estimate the color temperature of
a fluorescent lamp, whose color temperature is unknown, by the color
temperature estimating utilizing the color temperature DB 401 generated
by color temperature database generation.

Second Embodiment

[0080]Color processing of the second embodiment according to the present
invention will be described below. Note that the same components as in
the first embodiment are denoted by the same reference numerals in the
second embodiment, and a detailed description thereof will not be
repeated.

[0081]A process will be described below in which a color processing
apparatus uses a digital camera 114 to estimate the spectral type of a
fluorescent lamp whose spectral type is unknown. A process for estimating
the spectral type of a fluorescent lamp using the digital camera 114 can
be broadly divided into two processes. One is a process for generating a
spectral type DB of fluorescent lamp (to be referred to as spectral
type-database generation, hereinafter), and the other is a process for
estimating the spectral type of fluorescent lamp, whose spectral type is
unknown, by referring to the spectral type DB (to be referred to as
spectral type estimating, hereinafter).

[Spectral Type-Database Generation]

[0082]FIG. 12 is a view for explaining spectral type-database generation.
The spectral type-database generation includes four processes of white
paper capture S201, image analysis S202, spectral type obtaining S1101,
and a data link process S1102. Note that the white paper capture S201 and
image analysis S202 are the same as those in the first embodiment, and a
description thereof will not be repeated.

Spectral Type Obtaining

[0083]The spectral type obtaining S1101 is a process for obtaining the
spectral types of fluorescent lamps of all types used in the white paper
capture S201.

[0084]A spectral type includes three types of a broad-band type,
three-band type, and normal type, and can be obtained from the model of
fluorescent lamp or the like. In general, a light color symbol is
described in the model of fluorescent lamp and a spectral type can be
specified from the model. For example, when a light color symbol includes
"SDL", it indicates a broad-band type, and when a light color symbol
includes "EDL", it indicates a broad-band type particularly for color
evaluation. When a light color symbol includes "EX", it indicates a
three-band type, and when a light color symbol does not include any of
them, it indicates a normal type. In this manner, a spectral type can be
specified.

[0085]A spectral type may be specified using another method without
specifying it from a model or the like. For example, the light of a
fluorescent lamp may be measured using a spectroradiometer, and its
spectral distribution may be analyzed to specify a spectral type.

[0086]Information indicating the specification result (spectral type) and
information (a maker name, model, and the like) for identifying the type
of fluorescent lamp are input to the color processing apparatus via, for
example, a keyboard 111. A CPU 101 of the color processing apparatus
stores the input spectral type information and identification information
in a predetermined area of an HDD 106.

Data Link Process

[0087]The CPU 101 associates average x and y values corresponding to the
type of fluorescent lamp calculated in the image analysis S202 with a
spectral type corresponding to the type of fluorescent lamp input in the
spectral type obtaining S1101 based on the identification information to
generate a table an example of which is illustrated in FIG. 13. The CPU
101 stores the generated table in a predetermined area of the HDD 106 as
a spectral type DB 402 illustrated in FIG. 12 (data link process S1102).

[0088]In FIG. 13, "fluorescent lamp ID" indicates identification
information (ID) uniquely set for a fluorescent lamp of one type, and
LIGHT_MAX_COUNT indicates a maximum value of "fluorescent lamp ID", that
is, the number of types of fluorescent lamp.

[Spectral Type Estimating]

[0089]FIG. 14 is a view for explaining spectral type estimating. The
spectral type estimating includes three processes of white paper capture
S801, image analysis S802, and database referring S1303. Note that the
white paper capture S801 and image analysis S802 are the same as those in
the first embodiment, and a description thereof will not be repeated.

Database Referring

[0090]The database referring S1303 is a process executed by the CPU 101 of
the color processing apparatus for estimating, by referring to the
spectral type DB 402, a spectral type corresponding to estimation target
x and y values calculated in the image analysis S802, that is, the
spectral type of a fluorescent lamp 901 whose spectral type is unknown.

[0091]FIG. 15 is a flowchart for explaining the database referring S1303.
The database referring S1303 is different from the database referring
S803 illustrated in FIG. 11 in step S1410. More specifically, the CPU 101
obtains the spectral type of fluorescent lamp ID=MinID from the spectral
type DB 402, and executes a process such as displaying on a monitor 113
the obtained spectral type as the estimated spectral type of fluorescent
lamp 901 whose spectral type is unknown (S1410).

[0092]In this manner, it is possible to estimate the spectral type of a
fluorescent lamp whose spectral type is unknown by the spectral type
estimating utilizing the spectral type DB 402 generated by the spectral
type-database generation.

Modification of Embodiments

[0093]The first and second embodiments utilize the fact that the R, G, and
B values of the captured image of white paper captured while fixing the
WB parameter of a digital camera vary depending on an illuminant used in
capturing. Accordingly, the WB mode is not limited to "direct sunlight",
but other WB modes may be used as long as a WB parameter does not vary
but is fixed in that mode. In contrast, a mode such as "auto white
balance" in which a digital camera adjusts a WB parameter in accordance
with an illuminant cannot be used. Of course, a WB mode used in color
temperature/spectral type database generation needs to correspond with a
WB mode used in color temperature/spectral type estimating.

[0094]It is also possible to simultaneously estimate the color temperature
and spectral type of a fluorescent lamp whose color temperature and
spectral type are unknown by combining the color temperature DB 401 and
spectral type DB 402.

[0095]In addition, an illuminant to be estimated is not limited to a
fluorescent lamp if the color temperature DB 401 and/or spectral type DB
402 can be generated utilizing an illuminant having known illuminant
information.

[0096]According to the first and second embodiments, after the color
temperature DB 401 and/or spectral type DB 402 is generated, it becomes
possible to obtain the illuminant information of an illuminant having
unknown illuminant information by utilizing a general purpose image
capturing device such as a digital camera and white paper. At this time,
it is possible to obtain illuminant information in which an effect of a
lampshade and that of aging of an illuminant are reflected.

Third Embodiment

[0097]Color processing of the third embodiment according to the present
invention will be described below. Note that the same components as in
the first and second embodiments are denoted by the same reference
numerals in the third embodiment, and a detailed description thereof will
not be repeated.

[0098]A color temperature DB 401 and a spectral type DB 402 need to be
generated for each model of digital camera. Accordingly, color
temperature database generation and spectral type-database generation are
executed for respective models of digital camera to generate databases
for respective models as illustrated in FIG. 18, and the they are stored
in a predetermined area of an HDD 106.

[0099]FIG. 19 is a view illustrating an example of a user interface (UI)
displayed on a monitor 113 by color temperature/spectral type estimation
application software running on a color processing apparatus.

[0100]When the captured image of a white paper is input by white paper
capture S801, a CPU 101 displays it in a display region 1801. A user
manipulates a combo box 1802 for selecting the model of digital camera to
select the model of a digital camera used in the white paper capture S801
and presses an estimation button 1803. The CPU 101 refers to a database
corresponding to the selected model, displays an estimated color
temperature corresponding to the white paper image in a display section
1804, and displays an estimated spectral type in a display section 1805.

[0101]Note that instead of selecting the model of digital camera by a
user, the CPU 101 may specify the model of digital camera from
information (Exif data) appended to the captured image of the white
paper.

[0102]In addition, a color temperature/spectral type database may be
generated using a digital camera of a given type as a reference camera,
and the variation amount of a digital camera of another type with respect
to the reference camera may be stored in the database.

[0103]Furthermore, a database may be prepared not for each model of
digital camera but for each type (maker name and model) of white paper,
and a color temperature and spectral type may be estimated according to
the type of white paper and the model of digital camera. In this case, a
combo box for selecting the type of white paper is provided to the UI of
FIG. 19 in addition to the combo box 1802 for selecting the model of
camera.

Fourth Embodiment

[0104]Color processing of the fourth embodiment according to the present
invention will be described below. Note that the same components as in
the first to third embodiments are denoted by the same reference numerals
in the fourth embodiment, and a detailed description thereof will not be
repeated.

[0105]The fourth embodiment will exemplify a case in which a database
obtained by combining a color temperature DB 401 and a spectral type DB
402 corresponding to the model of a digital camera is stored in the ROM
or the like of the digital camera, and the color temperature and spectral
type of a fluorescent lamp are estimated using the "illuminant
information obtaining mode" of the digital camera.

[0106]FIG. 16 is a view illustrating the back surface of a digital camera.

[0107]A user manipulates a WB mode selection button 1501 to set the WB
mode of the digital camera. When the WB mode selection button 1501 is
pressed, the digital camera displays a WB mode selection menu as
illustrated in FIG. 17 on a liquid crystal monitor 1502.

[0108]The user manipulates selection keys 1503 to select an "illuminant
information obtaining mode" from the WB mode selection menu, and presses
a determination key 1504 to set the digital camera to the illuminant
information obtaining mode. Note that the WB parameter of the digital
camera set to the illuminant information obtaining mode fixes to a
predetermined value.

[0109]After this operation, when the user executes white paper capture
S801 under a fluorescent lamp whose color temperature and spectral type
are unknown, the CPU of the digital camera displays an estimated color
temperature and estimated spectral type on the liquid crystal monitor
1502.

[0110]Note that the "illuminant information obtaining mode" is not limited
to be selected as one of WB modes, but may be selected as one of
capturing modes. However, irrespective of the selection method used, the
WB parameter needs to be fixed.

Fifth Embodiment

[0111]Color processing of the fifth embodiment according to the present
invention will be described below. Note that the same components as in
the first to fourth embodiments are denoted by the same reference
numerals in the fifth embodiment, and a detailed description thereof will
not be repeated.

[0112]The first embodiment has exemplified a case in which the CPU 101
sets an ROI in the image analysis S202 and S802. The fifth embodiment
will exemplify a case in which a rectangular ROI of an arbitrary size is
set in an arbitrary position in a captured image in accordance with a
user's instruction. Setting an ROI in accordance with a user's
instruction is effective since when a shadow or an article other than
white paper is captured in the captured image of the white paper, it is
possible not to use that region in image analysis S202 and S802 in
accordance with user's decision.

[0113]FIG. 20 is a view illustrating an example of a user interface (UI)
displayed on a monitor 113 by color temperature/spectral type estimation
application software running on a color processing apparatus. The same
components as in the UI illustrated in FIG. 19 will not be described.

[0114]The UI includes four edit boxes 1901 to 1904 and displays an ROI
region frame 1905 in a display region 1801. The edit box 1901 is used to
display and input an x coordinate at the upper left corner of the ROI.
The edit box 1902 is used to display and input a y coordinate at the
upper left corner of the ROI. The edit box 1903 is used to display and
input a window width W of the ROI. The edit box 1904 is used to display
and input a window height H of the ROI.

[0115]When a user inputs numeric values in the four edit boxes, a CPU 101
displays the ROI region frame 1905 corresponding to the input position
and size in the display region 1801. The user can set an ROI with an
arbitrary position and size. Alternatively, the user can set an ROI with
an arbitrary position and size by manipulating a mouse 112 to adjust the
frame 1905 to a desired position and size.

[0116]Note that the shape of an ROI is not limited to a rectangular, and
it can be any shape as long as the region has an area equal to or larger
than a predetermined area. For example, when the shape of an ROI is a
circle, the ROI can be set using a combination of the center coordinates
(X, Y) and a radius R of the ROI.

Exemplary Embodiments

[0117]The present invention can be applied to a system constituted by a
plurality of devices (e.g., host computer, interface, reader, printer) or
to an apparatus comprising a single device (e.g., copying machine,
facsimile machine)

[0118]Further, the present invention can provide a storage medium storing
program code for performing the above-described processes to a computer
system or apparatus (e.g., a personal computer), reading the program
code, by a CPU or MPU of the computer system or apparatus, from the
storage medium, then executing the program.

[0119]In this case, the program code read from the storage medium realizes
the functions according to the embodiments.

[0120]Further, the storage medium, such as a floppy disk, a hard disk, an
optical disk, a magneto-optical disk, CD-ROM, CD-R, a magnetic tape, a
non-volatile type memory card, and ROM can be used for providing the
program code.

[0121]Furthermore, besides above-described functions according to the
above embodiments can be realized by executing the program code that is
read by a computer, the present invention includes a case where an OS
(operating system) or the like working on the computer performs a part or
entire processes in accordance with designations of the program code and
realizes functions according to the above embodiments.

[0122]Furthermore, the present invention also includes a case where, after
the program code read from the storage medium is written in a function
expansion card which is inserted into the computer or in a memory
provided in a function expansion unit which is connected to the computer,
CPU or the like contained in the function expansion card or unit performs
a part or entire process in accordance with designations of the program
code and realizes functions of the above embodiments.

[0123]In a case where the present invention is applied to the
aforementioned storage medium, the storage medium stores program code
corresponding to the flowcharts described in the embodiments.

[0124]While the present invention has been described with reference to
exemplary embodiments, it is to be understood that the invention is not
limited to the disclosed exemplary embodiments. The scope of the
following claims is to be accorded the broadest interpretation so as to
encompass all such modifications and equivalent structures and functions.

[0125]This application claims the benefit of Japanese Patent Application
No. 2008-106111, filed Apr. 15, 2008, which is hereby incorporated by
reference herein in its entirety.